﻿458 M. G. Quincke on the Capillary Phenomena 



on the surface of another liquid 1 consists in noticing in the drop 

 or bubble the change of form which accompanies the spreading. 

 , According to what has been said in § 25, the flat drop must in 

 spreading become flatter, or, to express it more accurately, the 

 magnitude K — k must diminish. The entire height of the drop 

 K will likewise diminish as soon as the angle 6 does not mate- 

 rially alter. 



In fact the experiments described in Section II. (§§ 11 to 14) 

 show this decrease. 



It follows from the summary given in § 10, Table X., that 

 Poisson's formula does not hold for mercury or water and a 

 series of liquids. It is thus in agreement with theory, and could 

 have been foretold by it, that bisulphide of carbon, olive-oil, oil 

 of turpentine, and petroleum spread themselves on flat air-bubbles 

 in water, as I have proved in § 12, or that water, olive-oil, and 

 oil of turpentine spread themselves on flat drops of mercury in 

 air, as I have proved in § 13. 



Absolute alcohol likewise spreads on a flat air-bubble in olive- 

 oil (§ 12), since also for alcohol and olive-oil the capillary con- 

 stant of the common surface, 0*226 milligrm., = a 12 , is <oi l — a< 2 , 

 which =3*760 milligrms. — 2*599 milligrms. =1*61 milligrm. 



The smallest value of the capillary constant a 12 is 0. In this 

 case the two liquids are miscible in all proportions, and equation 

 (3) always holds good ; the liquid 2 with smaller capillary con- 

 stant a 23 spreads on liquid 1 with greater capillary constant a, 3 . 



In fact it has been shown in § 14 that oil of turpentine 

 spreads on the surface of flat drops of olive-oil in water, or on 

 flat drops of bisulphide of carbon in water. 



Flat drops of water in olive-oil retain their form if permitted 

 to rest on a layer of mercury over which the olive-oil is poured. 

 K— k is the same for these drops as in flat bubbles of olive-oil 

 in water (§7); it becomes less as soon as alcohol is brought to 

 the boundary of oil and water — a proof that the alcohol spreads 

 itself out on this bounding surface, as might have been foretold 

 from the numbers of Table X. § 10 by help of the theory. 



In like manner olive-oil, oil of turpentine, and petroleum 

 (liquid 2), as was shown in § 14, spread themselves out on flat 

 drops of mercury (liquid 1) in water (liquid 3), as « 12 , for these 

 liquids (according to Table X. § 10) 34*19 milligrms., 25*54 mil- 

 ligrms., and 28*94 milligrms. respectively, is less thana 13 — a 23 ; 

 that is, less than 40*48 milligrms., 41*40 milligrms., and 38*75 

 milligrms. 



This spreading may also be observed in fused substances. 



In the case of fused metals, when they alloy with each other 

 in all proportions, a 12 also equals 0. 



If on a flat drop of gold or silver melted on charcoal, of which 



